Recently, many people are troubled with thinning hair, hair loss and baldness caused by, e.g., mental stress, changing eating habits, and aging. Because of this, the scalp-care market tends to expand. Such tendency is found in not only men but also women. Normal human hair periodically comes off and grows again. Such a hair cycle is repeated. About 90% of hair is in the anagen phase (i.e., the phase in which hair grows); whereas, about 10% of hair is in the telogen phase (i.e., the phase in which hair stops growing and falls off). Alopecia is caused by a mechanism where growth of hair follicle cells is suppressed and the hairs supposed to be in the anagen phase get in the telogen phase.
As male-pattern hair loss, male-pattern alopecia and alopecia areata are generally known well; while, as female-pattern hair loss, diffuse alopecia is known. As a cause of alopecia, not only a genetic cause but also aging, effects of male hormones, poor blood circulation, excessive hair care, heavy use of oral contraceptive, malnutrition, destruction of hair follicle bulb by lymphocytes are pointed out.
As a therapeutic agent for male-pattern alopecia, minoxidil (as an external preparation) and finasteride (as an oral therapeutic agent) are known. Minoxidil has an action to stimulate dermal papilla cells and causes them to secrete a growth factor, which promotes growth of hair matrix cells; while finasteride suppresses the action of type II 5α-reductase to prevent hair follicle miniaturization. As a therapeutic agent for alopecia areata, drugs such as adrenocortical hormone (a steroid), minoxidil and carpronium chloride are known.
The number of patent literatures concerning hair restoring agents and hair tonics is beyond 1,000 with the inclusion of, for example, JP Patent Publication (Kokai) No. 2012-092079 (Patent Literature 1), JP Patent Publication (Kokai) No. 2014-218479 (Patent Literature 2), JP Patent Publication (Kokai) No. 2014-129383 (Patent Literature 3), and JP Patent Publication (Kokai) No. 2013-193985 (Patent Literature 4). However, among drugs presently on the market, drugs effectively improving alopecia are small in number. A satisfactory hair growth effect cannot be usually obtained just by promoting blood circulation, improving scalp metabolism, and changing the hair cycle. As mentioned, overcoming alopecia can be said to be a difficult challenge.